Method for jointly optimizing noise reduction and voice quality in a mono or multi-microphone system
View Patent ↗The present technology provides adaptive noise reduction of an acoustic signal using a sophisticated level of control to balance the tradeoff between speech loss distortion and noise reduction. The energy level of a noise component in a sub-band signal of the acoustic signal is reduced based on an estimated signal-to-noise ratio of the sub-band signal, and further on an estimated threshold level of speech distortion in the sub-band signal. In embodiments, the energy level of the noise component in the sub-band signal may be reduced to no less than a residual noise target level. Such a target level may be defined as a level at which the noise component ceases to be perceptible.
1. A method for reducing noise within an acoustic signal, comprising:
receiving an acoustic signal;
separating the acoustic signal into a plurality of sub-band signals;
performing noise cancellation on a sub-band signal of the plurality of sub-band signals; and
applying a reduction value to the noise canceled sub-band signal to reduce an energy level of a noise component in the sub-band signal, the reduction value based on an estimated signal-to-noise ratio of the sub-band signal, and further based on an estimated threshold level of speech loss distortion in the sub-band signal.
2. The method of claim 1 , wherein applying the reduction value comprises performing noise suppression of the sub-band signal based on the reduction value.
3. The method of claim 2 , further comprising multiplying another reduction value to the sub-band signal to further reduce the energy level of the noise component.
4. The method of claim 1 , wherein applying the reduction value comprises multiplying the reduction value to the sub-band signal.
5. The method of claim 1 , wherein the energy level of the noise component in the sub-band signal is reduced to no less than a residual noise target level.
6. The method of claim 5 , further comprising:
determining a first value for the reduction value based on the estimated signal-to-noise ratio and the estimated threshold level of speech loss distortion;
determining a second value for the reduction value based on reducing the energy level of the noise component in the sub-band signal to the residual noise target level; and
selecting one of the first value and the second value as the reduction value.
7. The method of claim 6 , further comprising encoding the separated acoustic signal after applying the reduction value.
8. The method of claim 5 , wherein the residual noise target level is below an audible level.
9. The method of claim 6 , wherein the second reduction value is unity if the energy level of the noise component in the sub-band signal is less than the residual noise target level.
10. The method of claim 1 , wherein the reduction value is further based on estimated power spectral densities for the noise component and for a speech component in the sub-band signal.
11. A non-transitory computer readable storage medium having embodied thereon a program, the program being executable by a processor to perform a method for reducing noise within an acoustic signal, the method comprising:
receiving an acoustic signal;
separating the acoustic signal into a plurality of sub-band signals;
performing noise cancellation on a sub-band signal of the plurality of sub-band signals; and
applying a reduction value to the noise canceled sub-band signal to reduce an energy level of a noise component in the sub-band signal, the reduction value based on an estimated signal-to-noise ratio of the sub-band signal, and further based on an estimated threshold level of speech loss distortion in the sub-band signal.
12. The non-transitory computer readable storage medium of claim 11 , wherein applying the reduction value comprises performing noise suppression of the sub-band signal based on the reduction value.
13. The non-transitory computer readable storage medium of claim 11 , wherein applying the reduction value comprises multiplying the reduction value to the sub-band signal.
14. The non-transitory computer readable storage medium of claim 11 , wherein the energy level of the noise component in the sub-band signal is reduced to no less than a residual noise target level.
15. The non-transitory computer readable storage medium of claim 14 , further comprising:
determining a first value for the reduction value based on the estimated signal-to-noise ratio and the estimated threshold level of speech loss distortion;
determining a second value for the reduction value based on reducing the energy level of the noise component in the sub-band signal to the residual noise target level; and
selecting one of the first value and the second value as the reduction value.
16. The non-transitory computer readable storage medium of claim 14 , wherein the residual noise target level is below an audible level.
17. The non-transitory computer readable storage medium of claim 15 , wherein the second reduction value is unity if the energy level of the noise component in the sub-band signal is less than the residual noise target level.
18. The non-transitory computer readable storage medium of claim 11 , further comprising multiplying another reduction value to the sub-band signal to further reduce the energy level of the noise component.
19. A system for reducing noise within an acoustic signal, comprising:
a frequency analysis module stored in a memory and executed by a processor to receive an acoustic signal and separate the acoustic signal into a plurality of sub-band signals;
a noise canceller module stored in the memory and executed by the processor to perform noise cancellation on a sub-band signal of the plurality of sub-band signals; and
a noise reduction module stored in the memory and executed by the processor to apply a reduction value to the noise canceled sub-band signal to reduce an energy level of a noise component in the sub-band signal, the reduction value based on an estimated signal-to-noise ratio of the sub-band signal, and further based on an estimated threshold level of speech loss distortion in the sub-band signal.
20. The system of claim 19 , wherein the noise reduction module performs noise suppression of the sub-band signal based on the reduction value.
21. The system of claim 19 , wherein the noise reduction module multiplies the reduction value to the sub-band signal.
22. The system of claim 19 , wherein the energy level of the noise component in the sub-band signal is reduced to no less than a residual noise target level.
23. The system of claim 19 , wherein the reduction value is further based on input received via an application program interface for the noise reduction module.